Don't get all the troll hate. Out of all the races (Horde, that is), a troll seemed best suited for a hunter. Crouching from time to time, sniffing tracks or w/e. Their story is pretty much awesome, as well.

I cannot play pandas, gnomes or goblins. Pandas - I hate them passionately, the other two I hate because I just can't get myself to play runts.

I avoid any race that is overpopulated, namely Humans for Alliance and Belves for Horde.
I generally choose race mostly by aesthetics and animation (2H swing and casting animations are most important, since that is what I'm going to see 99% of the time when not idle).
I don't like races without shoes, especially for plate classes (so worgen and trolls are the biggest offenders; tauren, draenei, undead and pandaren are tolerable)

Humans and both elves. Humans for awful animations and crappy, boring visuals. Elves for obvious reasons.
For playing I prefer Draenei females in Alliance/Undead males+orc females in Horde.
Pandarens are nice too, both genders. Just don't get it, why the red female gets the tail, and others don't.

I had a gnome warlock as alt back in Vanilla, reached level 45 (Bit more work back then :P ), and couldn't stand the whole gnome style anymore, the animations, the noises, i re-rolled that alt as a human (No race-change then either >_< ) and never looked back...

Orcs. Males, hunchback, ugly, bad animations, ugly models, everything. I have never ever played one, except 2 quests in the starting zone, which after I decided I would never touch that race again.
Females.... Don't even get me started. Would never make one.